﻿J. 
  W. 
  JTJDD 
  ON 
  THE 
  SECONDARY 
  ROCKS 
  OE 
  SCOTLAND. 
  299 
  

  

  Old 
  Red 
  Sandstone 
  is 
  admirably 
  represented, 
  in 
  all 
  its 
  divisions, 
  

   both 
  by 
  sedimentary 
  and 
  igneous 
  products 
  ; 
  while 
  the 
  Carboni- 
  

   ferous 
  and 
  Permian 
  (?) 
  also 
  find 
  representatives 
  in 
  rocks 
  of 
  the 
  latter 
  

   class. 
  As 
  I 
  shall 
  show 
  in 
  the 
  present 
  memoir, 
  we 
  have 
  fragmentary 
  

   but 
  almost 
  consecutive 
  examples 
  of 
  all 
  the 
  Mesozoic 
  formations, 
  

   from 
  the 
  Trias 
  to 
  the 
  highest 
  rocks 
  of 
  the 
  Cretaceous 
  series. 
  In 
  the 
  

   Tertiary 
  epoch 
  we 
  have 
  the 
  felspathic 
  igneous 
  rocks 
  representing 
  

   the 
  Eocene 
  period, 
  the 
  basaltic 
  rocks, 
  the 
  Miocene, 
  and 
  the 
  smaller 
  

   scattered 
  eruptions 
  of 
  the 
  " 
  puys 
  " 
  the 
  Pliocene 
  ; 
  while 
  of 
  the 
  

   Pleistocene 
  period 
  the 
  interesting 
  glacial 
  deposits 
  of 
  the 
  Highlands 
  

   supply 
  us 
  with 
  a 
  sufficient 
  record. 
  Thus 
  we 
  arrive 
  at 
  a 
  basis 
  for 
  

   the 
  construction 
  of 
  a 
  true 
  geological 
  map 
  of 
  the 
  Scottish 
  Highlands 
  ; 
  

   but 
  the 
  actual 
  performance 
  of 
  this 
  task 
  is 
  one 
  which 
  will 
  demand 
  a 
  

   vast 
  expenditure 
  of 
  time 
  and 
  effort. 
  

  

  4. 
  Light 
  thrown 
  on 
  some 
  problems 
  of 
  Physical 
  Geology 
  by 
  the 
  

   Volcanic 
  Rocks 
  of 
  the 
  Highlands. 
  — 
  The 
  admirable 
  labours 
  of 
  those 
  

   pioneers 
  of 
  Scottish 
  geology, 
  Hutton, 
  Playfair, 
  Webb 
  Seymour, 
  

   James 
  Hall, 
  and 
  Macculloch, 
  have 
  clearly 
  demonstrated 
  the 
  relations 
  

   which 
  exist 
  between 
  the 
  granitic 
  and 
  the 
  associated 
  strata 
  of 
  the 
  

   Highlands. 
  On 
  the 
  other 
  hand 
  the 
  researches 
  of 
  Scrope 
  among 
  the 
  

   extinct 
  volcanoes 
  of 
  Central 
  France, 
  supplemented 
  as 
  these 
  have 
  

   been 
  by 
  the 
  observations 
  of 
  Darwin, 
  Lyell, 
  and 
  a 
  host 
  of 
  other 
  

   geologists, 
  in 
  the 
  most 
  widely 
  scattered 
  districts, 
  have 
  thrown 
  much 
  

   light 
  upon 
  the 
  structure 
  of 
  modern 
  volcanoes 
  and 
  upon 
  the 
  nature 
  

   and 
  succession 
  of 
  the 
  phenomena 
  which 
  accompany 
  their 
  formation. 
  

   In 
  the 
  rocks 
  of 
  the 
  Hebrides 
  we 
  find 
  the 
  means 
  of 
  connecting 
  

   these 
  two 
  series 
  of 
  observations, 
  and 
  thus 
  of 
  arriving 
  at 
  a 
  complete 
  

   theory 
  of 
  the 
  action 
  of 
  the 
  igneous 
  forces 
  operating 
  under 
  different 
  

   conditions. 
  

  

  The 
  characteristics 
  of 
  Stigmarice 
  and 
  Sigillarice 
  respectively 
  were 
  

   known 
  to 
  palaeontologists 
  long 
  before 
  the 
  discovery 
  of 
  a 
  section 
  in 
  

   the 
  Coal-measures 
  enabled 
  them 
  to 
  be 
  identified, 
  in 
  their 
  true 
  

   relations, 
  as 
  the 
  roots 
  and 
  trunks 
  of 
  the 
  same 
  plant. 
  Similarly 
  

   physical 
  geologists 
  have 
  separately 
  studied 
  the 
  features 
  of 
  Volcanic 
  

   and 
  Plutonic 
  rocks, 
  which 
  the 
  wonderful 
  sections 
  of 
  the 
  Hebrides 
  

   now 
  warrant 
  us 
  in 
  affirming 
  to 
  have 
  the 
  closest 
  connexion 
  — 
  the 
  great 
  

   intrusive 
  masses 
  being, 
  as 
  it 
  were, 
  the 
  roots 
  of 
  a 
  tree 
  of 
  which 
  the 
  

   stem, 
  branches, 
  and 
  leaves 
  are 
  represented 
  by 
  the 
  dykes, 
  lava 
  

   streams, 
  and 
  cinder 
  piles 
  of 
  great 
  volcanic 
  cones. 
  

  

  Prom 
  the 
  active 
  volcanoes 
  of 
  Etna, 
  Vesuvius, 
  and 
  Skaptar 
  Jokul, 
  

   the 
  step 
  to 
  the 
  ruined 
  piles 
  of 
  the 
  Mont 
  Dore 
  and 
  the 
  Cantal 
  is 
  an 
  

   easy 
  one 
  : 
  and 
  with 
  these 
  last 
  we 
  have 
  but 
  little 
  difficulty 
  in 
  

   perceiving 
  the 
  parallelism 
  of 
  the 
  phenomena 
  displayed 
  by 
  the 
  rocks 
  

   in 
  the 
  central 
  mountain-group 
  of 
  Mull. 
  Prom 
  the 
  condition 
  of 
  the 
  

   volcanic 
  rocks 
  in 
  Mull 
  to 
  that 
  in 
  Skye 
  the 
  transition 
  is 
  obvious, 
  and 
  

   from 
  the 
  latter 
  to 
  Beinn 
  Nevis, 
  and 
  thence 
  to 
  the 
  granitic 
  bosses 
  of 
  

   Cairngorm, 
  the 
  Moor 
  of 
  Kannoch, 
  and 
  the 
  Ross 
  of 
  Mull, 
  can 
  easily 
  

   be 
  made 
  ; 
  nor 
  will 
  any 
  difficulty 
  be 
  experienced 
  in 
  passing 
  from 
  

   these 
  latter 
  to 
  the 
  wide- 
  spreading 
  tracts 
  of 
  granite, 
  such 
  as 
  that 
  of 
  

   Leinster. 
  

  

  